This disclosure relates to lubrication, and more particularly a method and apparatus for monitoring journal bearing lubrication.
A gas turbine engine typically includes a fan section, a compressor section, a combustor section and a turbine section. Air entering the compressor section is compressed and delivered into the combustion section where it is mixed with fuel and ignited to generate a high-speed exhaust gas flow. The high-speed exhaust gas flow expands through the turbine section to drive the compressor and the fan section.
A speed reduction device such as an epicyclical gear assembly may be utilized to drive the fan section such that the fan section may rotate at a speed different than the turbine section so as to increase the overall propulsive efficiency of the engine. In such engine architectures, a shaft driven by one of the turbine sections provides an input to the epicyclical gear assembly that drives the fan section at a reduced speed such that both the turbine section and the fan section can rotate at closer to optimal speeds. Such gear assemblies may include journal bearings.
Air moving through a non-operating gas turbine engine may rotate a fan of the fan section of the gas turbine engine, which causes rotation in the gear assembly. This is known as “windmilling” and it can occur due to either headwinds or tailwinds. If the gas turbine engine is shut down and parked on the ground when windmilling occurs, that is known as “ground windmilling.” Even though the engine is not operating during windmilling, rotation of the gear assembly requires lubricant. Journal bearings are particularly sensitive to lubrication deprivation. Thus, an auxiliary lubrication pump has been utilized that is driven by rotation of the fan. Through this arrangement, rotation of the fan drives the auxiliary lubrication pump to provide lubrication during windmilling, even when the engine is shut down.
During normal engine operation, a main lubrication pump is rotationally driven by a high speed spool, supplying lubricant to the gear assembly. During windmilling, the high speed spool is not rotationally driven. The auxiliary lubrication pump is driven whenever the fan is rotationally driven (e.g., during windmilling). In one example, the auxiliary lubrication pump is located in close proximity to the fan, and is driven by a fan shaft.